The following disclosures may be relevant to various aspects of the present invention and may be briefly summarized as follows:
Many testers and test methods for evaluating the frictional wear characteristics of materials and lubricants are known in the art. The prior art reference entitled “Polymers, An Encyclopedic Sourcebook of Engineering Properties”, Encyclopedia Reprint Series, John Wiley & Sons Inc., copyright 1987 pgs. 8-11, discloses a variety of devices and ASTM standards for test procedures for frictional wear.
Tribology Data Book (Techno System Shuppan, 1991). pgs. 195-205 describes various types of abrasion tests and their features, including pin-on-disk type, thrust cylinder type and block-on-ring type testers. The reference also mentions that it is common for measurement to be carried out under a fixed contacting load and a fixed friction speed.
JP-A 54-145584 is aimed at the measurement and evaluation of frictional resistance in a test specimen subjected to a fluctuating load under the same conditions as an actual piece of equipment that employs a reciprocating sliding mechanism. This reference discloses a tester, which uses an eccentric cam in order to vary as desired the sliding velocity, the contacting load, and the fluctuating load and period.
U.S. Pat. No. 4,939,922 to Smalley et al. discloses a technique for measuring the sliding characteristics between two test specimens that slide relative to each other while remaining in mutual contact. One of the test specimens being rotated by means of a rotary drive unit via an eccentric cam and the other test specimen being pressed against the first test specimen by an elastic body.
The testers and test methods disclosed in the prior art have the drawback that the sliding results obtained from the tests do not always conform well with the sliding characteristics of components in actual pieces of (e.g. commercial) equipment. This is believed to be attributable to the following reasons. In commercial or actual pieces of equipment: (1) the load and the sliding velocity are often not uniform, but instead vary periodically within a range; (2) because the test is carried out with the test specimens constantly in a state of mutual contact, the frictional heat generated builds up in the area of contact and the frictional wear behavior is strongly affected by the ensuing rise in temperature; and (3) because powder generated by abrasion builds up on the contact surfaces, the measured amount of wear does not directly represent the wear properties of the material.
Furthermore, in sliding-type abrasion tests in which a lubricating oil or grease is applied to the contact surface of the test specimen, the coefficient of friction is quite low, very little wear occurs, hence clear differences are often not obtained in measurement making it difficult to achieve worthwhile test results. In various electrical products for industrial or consumer applications, including drive system motors employed in automotive electrical components, sliding mechanism components are generally used with a lubricating oil or grease on the contact surfaces. Accordingly, there is a desire for an abrasion tester which can measure and evaluate the frictional wear characteristics of such components in a state that is the same as or similar to the conditions of actual use and which provides a higher reliability that makes it possible to predict the life of a product, thus enabling suitable material selection or design to be carried out.